Engine fuel injectors may become degraded and start to leak fuel into a corresponding engine cylinder. Such leaky fuel injectors may degrade fuel consumption, increase emissions, and cause engine start issues. Attempts to address the problem of fuel injector leaks may include corrective actions that are implemented while the engine is running In one example approach, a lean air-fuel mixture is delivered to a cylinder with the leaking fuel injector to compensate for the presence of leaked fuel and/or other cylinders may be operated with a lean air-fuel ratio.
However, the inventors herein have recognized an issue with the above approach in that the above mentioned corrective actions may be implemented only when the engine is running and not during engine off conditions. In particular, relying on engine operating corrective actions may be problematic in vehicles configured to perform automatic stops. For example, a vehicle travelling in congested traffic may encounter frequent start and stop events. During such idle stops, a leaky fuel injector may cause problems during subsequent engine restart, including engine misfire, stumble, hydro lock, etc., and degrade vehicle emissions. Fuel leak during prolonged idle stops may also allow fuel to seep past the piston rings and into the crankcase, wherein it may dilute the engine oil and diminish engine lubrication, increasing the possibility of engine damage.
To at least partially address fuel injector leaks in vehicles, such as those with prolonged idle stops, a method for operating an engine is provided, comprising identifying a cylinder of an engine with a fuel injector leak, and at or after engine shutdown, positioning the engine to a selected engine position based on the identified cylinder such that an exhaust valve of the identified cylinder is at least partly open. By positioning the identified cylinder with the exhaust valve open during idle stops, the leaked fuel from the injector may vaporize from the hot cylinder wall and escape by natural diffusion through the open exhaust valve to a downstream catalyst, where the leaked fuel vapors may be converted prior to releasing to atmosphere. As one example, a starter motor may be used to re-position the engine based on the identified cylinder with leaky fuel injector, such that the exhaust valve of the identified cylinder is at least partly open during engine idle stops.
The present description can provide several advantages. Specifically, the method can reduce engine emissions, engine misfire, engine roughness, and engine damage in vehicles used for frequent city driving with prolonged idle stops.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.